It has been proposed heretofore to tag an explosive by enclosing within a blasting cap a source of sulfur hexafluoride (SF.sub.6) vapor absorbed in a fluoropolymer. Such a taggant is described in U.S. Pat. No. 3,991,680 issued Nov. 16, 1976 to R. N. Dietz et al.
While this technique avoids the prior reliance upon physical searches, X-Rays, and dogs trained to sniff out the presence of certain types of explosive materials, its usefulness has been limited by major disadvantages. Sulfur hexafluoride vapor is present in ambient air in readily detectable amounts (0.5.+-.0.1 parts per trillion). It is used to a large extent by commercial and industrial processes. Thus electronic detectors or "sniffers" used to detect the presence of SF.sub.6 often produce misleading indications of the presence of explosives, when none are present. Furthermore, the high background concentrations of SF.sub.6 might limit the detection of explosives containing this taggant in certain detection situations. Secondly, the high intrinsic vapor pressure of SF.sub.6 (343 psia at 25.degree. C.) interfers with the delayed timing mechanisms of blasting cap detonators, thus precluding the use of SF.sub.6 as a vapor taggant in timed blasting cap detonators.